Snap acting device



Oct. 25, 1949. o. H. KAMINKY SNAP ACTING DEVICE 2 Sheets-Sheet 1 FiledFeb. 6, 1946 Oct. 25, 1949; o. H. KAMINKY 2,486,033

SNAP ACTING DEVICE Filed Feb. 6, 1946 2 Sheets-Sheet 2 Patented Oct. 25,1949 UNITED STATES PATENT OFFICE SNAP ACTING DEVICE Application February6, 1946, Serial No. 645,816

13 Claims. 1

My invention relates to electrical snap switches of the compactprecision type, and is more particularly concerned with an improvedconstruction which eliminates the many rivets and screws employedinconventional switches of this type to hold the "parts together. Byreferring to the switch of niy'invention as being of the precisiontype," I means one which operates in responseto very slight movement ofan operating plunger and one 'ich is -intended to operate consistentlyat the sai'iiefiposition of the plunger. One comto such slight motionand pressure, extreme care and accuracy has been required in itsmanufacture inasmuch as the operation of the conventional switch can beimpaired very materially by slight misadjustments of its mechanism.Nonuniform performance resulting from such misadjustment is unavoidableto a certain extent in the conventional switch where individual parts ofthe operating mechanism are assembled and held within the housing bymeans of a number of screws or rivets.

A primary object of my invention, therefore, is the provision of aswitch mechanism which can be assembled without the use of a singlescrew or'rivet to hold any individual part in place, the parts beinginserted in slots and recesses molded in the switch housing, all partsbeing maintained within these slots and recesses by a cover plate whichis held in place by any suitablesfastening means, as for instance asingle rivet.

Another object of my invention is the provision of a precision switchwhich can be assembled quickly by unskilled labor without detriment toits performance characteristics, thereby permitting it to bemanufactured inexpensively in large quantities. 7

An important advantage resulting from my improved construction is that Ican dispense with the extra housing volume required in conventionalswitches to accommodate the internal high capacity switch of hithertounknown coinpactness. My switch is so compact that it may be used, forexample, in certain small instruments where the use of a switch has longbeen desirable but has been heretofore impracticable with the relativelybulky switches available; thus my invention represents a significantstep forward in the art of instruments as well as that of switches.

Other objects and advantages will appear from the following descriptionand the accompanying drawings, in which- Figure 1 is a side view,constituting a plane section through the cover-housing interface, of asingle pole double throw switch showing one modification of myinvention;

Fig. 2 is a side view similar to Figure l'showing the plunger depressedand the movable contacts in the opposite position;

Fig. 3 is a section on the line 3-3of Figure-1, but showing the cover inplace;

Fig. 4 is a section on the line 4-4 of Figure 1, showing the cover inplace;

Fig. 5 is a section on the line 5-5 of Figure 1, showing the cover inplace;

Fig. 6 is a section on the line 6-6 of Figure 1, showing the cover inplace;

Fig. 7 is a side view, constituting a plane section through thecover-housing interface, of a single pole double throw switch showinganother modification of my invention;

Fig. 8 is a side view similar to Fig. '7 showing the plunger depressedand the movable contacts in Like reference characters refer to likeparts throughout the drawings. a

The switch illustrated is generally similar to that shown in mycopending application entitled Snap acting control mechanism, Serial No.640,725, filed January 12, 1946. Referring now in detail to thedrawings, the modification shown I in Figs. 1-6 comprises a housinggenerally designated 2| having: the body or base portion 22 havingupstanding end walls 23 and 24 and side walls 26 and 21; the cover plate28 having the transversely extending positioning boss 30 adapted to helpmaintain the cover plate in place upon the open side of the housing;first and second terminal members 29 and 3|, carrying spaced stationarycontacts or stops 32 and 33 respectively, and extending throughapertures 34. and 36 in the end wall 24; a third terminal member ormounting bracket 31 extending through aperture 36 in the side wall 21and which in this embodiment comprises offset mounting portionsinterconnected by a bridging portion; the actuator member 39 having theknife edge 4| pivotally engaging the groove 42 formed in terminal member31; an overcenter snap spring system comprising an approximatelyrectangular-shaped resilient metal strip generally designated 43, havingcompression element 44 pivotally engaging the groove 46 formed in theterminal member 31, the tension elements 41, the end portion 48pivotally engaging the groove 49 formed in the actuator 39, the distancebetween the grooves or recesses 46 and 49 being sufiiciently greaterthan the unstressed distance between the end portion 48 and the end ofthe compression element 44 that when assembled as shown the compressionelement is bowed upwardly and stressed in compression and the tensionelements are stressed'in tension; the plunger member 5I reciprocablewithin the aperture 52 formed in side wall 26 and having the enlargedinner end portions 53 to maintain it within the housing. Normally theactuator or lever 39 will be maintained resiliently pressed against theinner end surface 54 of the plunger by the spring member 43. Theterminal members 29, 3| and 31 will be fitted with suitable means forconnecting external wires, as for instance with the screws 56.

Transversely extending lugs 51 are formed on the inner end portions ofthe terminal members 29 and 3| and are closely fitted within therecesses 56 formed in the housing and cover plate. The inner end ormounting portion 35 of terminal member 31 is closely fitted within therecess 40 formed in the wall 26 of the housing. The engagement of theinner end portions by these recesses, combined with the closely fittingengagement of their intermediate portions within the apertures 34, 36and 38, serve to secure the terminal members immovably in their properpositions. It will be obvious that with the terminal members so securedthe spring member 43, actuator 39 and plunger 5| will seek the positionsshown in Fig. 1.

In assembling the switch the advantages of this construction whicheliminates the conventional screws and rivets are at once apparent.Since each of the four apertures 34, 36, 38 and 52 have one side open inthe direction of the housing open side, assembly is readily carried outas follows: The plunger 5| is inserted within the aperture or slot 52:the spring member 43, the actuator 39 and the terminal member31 arefitted together outside the housing as a sub-assembled unit which isthen inserted so the housing engages the terminal member 31 at therecess 40 and at the a erture 38: terminal members 29 and 3| are thenfitted within the apertures 34 and 35 with l gs 5 engaging housingrecesses 58; and cove plate 28 is attached by any suitable means as by arivet (not shown) fitted within the housin rivet hole 59 and within asimilar hole (not shown) in the cover plate, the cover plate beingmaintained from rotation about the rivet hole by the engagement of thepositioning boss 36 within the space between the terminal members 2'1and 3|; and by engagement of termina lugs 51 within cover plate recesses58. The boss 30 serves additionally to help maintain the terminals 29and 3| in properly spaced relation.

The position or the parts shown in Figure 1 is the normal position ofthe switch mechanism, the movable contact 20 being disposed inengagement with the stationary contact 32. When the plunger 5| isdepressed the actuating member 39,is depressed from the position ofFigure 1 to the position of Fig. 2, during which movement the groove 49on the actuating member is moved downward toward the compressioncenterline of the spring member against the compression of thecompression element 44. In the particular switch shown. the axis orposition of maximum stress is reached when the groove 46 is coplanarwith the tension members 41 and when the tension members are moveddownwardly through this axis the spring member reverses its position tothat shown in Fig. 2 with a snap movement; similarly, when thedepressive force in the plunger is released the spring member will moveupwardly under the influence of fiexural forces stored in it until thetension elements pass the above-mentioned coplanar position whence itmoves to the position shown in Fig. 1, by snap action.

The modifica ion shown in Figs. '1 to 12 is substantially the same inconstruction and operation as that shown in Figs. 1 to 6 except that theactuator moves the compression element I44 (instead of the tensionelements 41) to snap the spring member between the stationary contacts.The

modification shown in Fig. '1 is of the center plunger type which may bepreferred for particular applications; and the terminal members extendthrough only the end walls of the housing whereby the switch may beconveniently employed in a flush mounted position against a wall.

Referring, now, specifically to Figs. '7 through 12, this modificationcomprises a housing generally designated I2I having: the body or baseportion I22 having upstanding end walls I23 and I24 and side walls I26and I21; the cover plate I26 having the transversely extendingpositioning boss I36 adapted to hold the cover plate in place upon theopen side of the housing; first and second terminal members I29 and I3Icarrying spaced stationary contacts or stops I32 and I33 respectively,and extending through apertures I34 and I36 in the end wall I24; a thirdterminal member I31 extending through aperture I 36 in the end wall I23;an actuator member I39 having the knife edge I4I pivotally engaging thegroove I42 formed in the terminal member I31; an overcenter snap springmember comprising an approximately rectangular shaped resilient metalstrip designated I43, having compression element I44 pivotally engagingthe groove I46 formed in the actuator member I39, tension elements I41,the end portion I48 pivotally engaging the groove I49 formed in theterminal member I31, the distance between the grooves I46 and I49 beingsufliciently greater than the unstressed distance between the endportion I48 and the end of the compression element I44 that whenassembled as shown the compression element is bowed downwardly andstressed in compression and the tension elements are stressed intension; the plunger member I5I reciprocable within the aperture I52formed in the side wall I26 and having the enlarged inner end portionsI53 to maintain it within the housing. Normally, the actuator I39 willbe maintained resiliently pressed against the inner end surface I54 ofthe plunger by th spring member I43. The terminal members I29, I3I andI31 will be fitted with suitable means for connectpended claims.

' the inner end portions of the terminal members I23 and I3I and arclosely fitted within the receases Ill formed in the housing and in thecover plate. The inner end portion I33 of terminal member I3! is closelyfitted within the recess I4Il formed in the side wall I23. Theengagement of the inner end portions by thes recesses, combined with theclosely fitting engagement of their intermediate portions within theapertures I34, I33 and I33, serve to secure the terminal membersimmovably in their proper positions. It will be obvious that with theterminal members so secured the spring member I43, actuator I33 andplunger I3I will seek the positions shown in Fig. '7. v Assembly of thecenter-plunger switch is carried out in the same manner as thatdescribed for the end-plunger switch, the spring member I43, theactuator I33 and the terminal member I31 being fitted together outsidethe housing and inserted as a sub-assembled unit.

The position of the parts shown in Fig. 7 is the normal position of theswitch mechanism, the movable double-faced contact I20 being disposed inengagement with the stationary contact I33. When the plunger II isdepressed the actuating member I33 is depressed from the posi tion ofFig. '7 to the position of Fig. 8, during which movement the groove I46on the actuating member is moved downward toward the compression centerline of the spring member against the compression of th element I44. Inthe particular switch shown, the axis or position of maximum stress isreached when the groove I46 is coplanar with the tension members I41 andwhen the groove is moved downwardly through this axis, the springreverses its position to that shown in Fig. 8 with a snap movement;similarly, when the depressive force on the plunger is released, thecompression element will move upwardly under the influence of fiexuralforces stored in it until the groove I46 passes the above mentionedcoplanar position whence the spring member will move to the positionshown in Fig. ,7 by snap action.

I The end plunger switch isconstructed to be self-returning to the Fig.1 position by placing th contact or stop 33 so the plane containingtension elements 41 cannot cross the pivot 42.

It may be constructed to be non-returning either by raising the pivot 42or by lowering the contact or stop 33 so that in passing between theFigures 1 and 2 positions the plane will cross that pivot.

Similarly, the center plunger switch is constructed to be self-returningto the Fig. '7 position by placing the contact or stop I32 so the planecontaining tension elements I41 cannot cross the pivot I4I. It may beconstructed to be non-re-' turning either by raising the pivot I4I or byraising thecontact or stop I 32 so that in passing between the Figures 7and 8 positions the plane will cross that pivot.

While I have thus described two specific embodiments of my invention Iam aware that numerous alterations and changes may be made thereinwithout materially departing from the spirit of the invention and thescope of the ap- For example, instead of a single pole double throwswitch as illustrated in both embodiments, my invention is equallyapplicable to other contact combinations, such as a single pole singlethrow switch, or a double pole double throw switch. Furthermore, in somemodifications the reciprocable plunger SI maybe replaced by other meansfor moving the actuator member, as, for instance, in service where it isdesired to seal the housing against the entrance of dust or moisture,the actuator 39 may be actuated through a diaphragm or bellows (neithershown) fitted into the housing, or the actuator may be actuated by amagnetic element (not shown) positioned exteriorly of the housing, or byany other suitable operating means. In some instances it may bedesirable for special purposes to dispense with some or all of the lugs51 which are engaged by the recesses 58 for under some serviceconditions it may be sufficient to secure the terminal members, or someof them, within the housing solely by engagement with the slots formedin the walls; a but for the best advantage it will be preferable wherepossible to mount the terminal members securely at their interior endportions in addition to fitting them into wall apertures.

I claim:

1. In an electric snap switch the combination 'of: a housing ofinsulating material including a cover plate and a body with an open sidenormally closed by the cover plate; said housing having aperturestherein adjacent the body-cover interface fittedly engaging terminalmembers and a reciprocable plunger, two of said terminal members havingstationary contacts attached thereto; each of said apertures having anopen side at said body-cover interface whereby saidterminal members andsaid plunger are insertable into said housing through said housing openside; said two terminal members being secured in said housing bytransversely extending lugs on said terminal members engaging recessesformed in said cover plate and in said body portion; an actuating memberpivotally engaging a third of said terminal members and movable by saidplunger; a spring member made of a resilient metallic strip havingspaced side portiolgs comprising elongated tension elements and havingend portions connecting said tension elements, one of said spring memberend portions having an inwardly extending compression element, saidspring member being so fitted within said housing and its parts soproportioned. and so dimensioned that its compression element ispivotally compressed upon said third terminal member and the springmember end portion opposed to said compression element is pivotallyengaged with said actuator member in such a manner as to stress saidtension elements in tension whereby, when said plunger is depressed,said actuating member will move said tension elements to move saidspring member to carry said movable contact from one of saidstational'y'contacts to the other in a snap action manner.

2. An electric snap switch, comprising a housing including a, coverplate and a body with an open side normally closed by the cover plate,said housing having first, second and third spaced slots opening at thebody cover interface, terminal members shaped to be received in saidfirst and second slots, means integral with said terminals adapted toco-act with the housing to position the terminals therein, saidterminals being insertable in said housing through the open sidethereof, a spring member having a contact movable between said terminalmembers, said spring member having an axis of maximum stress and beingformed from a resilient metal strip, said spring member having thegeneral shape of a rec tangular frame comprising long sides and short 7sides interconnecting opposite ends of the long sides, one of saidshorter sides having a portion extending inwardly of said frame betweenthe long sides, a bracket defining another terminal member and shaped tobe received in said third slot and supporting said inwardly extendingportion so that the latter is in compression, an actuating member shapedto support the other of saidshort sides so that the long sides are undertension, said bracket pivotally supporting said actuating member so thatsaid bracket, said actuating member and said spring form a unitinsertable in said housing through the open side thereof, and meansextending through said housing engaging said actuating member to movesaid spring member through its axis of maximum stress and thereby movesaid movable contact between said terminal members witha snap action,

3. An electric snap switch, comprising a housing including a cover plateand a body with an open side normally closed by the cover plate, saidhousing having first, second and third spaced slots opening at the bodycover interface, terminal members shaped to be received in said firstand second slots, means integral with said terminals adapted to coactwith the housing to position the terminals with respect thereto, saidterminals being insertable in said housing through the open sidethereof, a spring member having a contact movable between said terminalmembers, said spring member having an axis of maximum stress andcomprising spaced tension members interconnected at opposite ends, one

a pivotally mounted rigid lever, movable between preselected positions,and an overcenter snap spring system comprising a compression member andspacedtension members, said tension members being interconnected atopposite ends, one of said interconnected ends being free to movebetween preselected positions with a snap action, said compressionmember having one end interconnected with said free end and the oppositeend pivotally supported by said bracket and said other interconnectedend of the tension members being pivotally supported by said leverwhereby movement of said lever about its pivotal mounting shifts saidtension member relative to the compression member to move said free endbetween the preselected positions.

6. In a snap action device, the combination of a snap spring systemcomprising spaced tension members interconnected at a first end and asecond end thereof and a compression member intermediate said tensionmembers and interconnected at one end with said first end, said firstend being free to move between preselected positions with a snap action,a bracket disposed between said tension members comprising mountingportions atsubstantially right angles to the plane of the tensionmembers and offset with respect to each other and a"bridging portioninterconnecting the offset portions and in substanof said ends beingfree to move between said tersertable in said housing through the openside thereof, means disposed between said bracket and said housing toposition said bracket therein, and a plunger mounted on said housing andengaging said actuating member to move said tension members relative tocompression member through the axis of maximum stress and thereby efiectsnap movement of said movable ,contact between said first mentionedterminal members.

4. In a snap action switch, the combination of a support, opposed stopson said support, a

bracket mounted on said support in spaced relation with said stops, arigid lever pivotally mounted on said bracket for movement toward oraway from said support, means for limiting the movement of said lever,and a snap spring system having an axis of maximum stress and comprisinga compression member and a tension member, one end of each of saidtension and compression members being free to move between said opposedstops, the opposite end of said compression member being pivotallysupported by said bracket and the opposite end of said tension memberbeing pivotally engaged by said lever whereby movement of said levershifts said tension member relative to said compression member throughsaid axis of maximum stress to move said free ends between the opposedstops with a snap action. I

5. In a snap action switch, the combination tially parallel relationwith the plane of the tension members, means for rigidly supporting eachof said mounting portions, one of said mounting portionshaving a recessadjacent one side of the bridging portion pivotally receiving theopposite end'of the compression member, said other mounting portionhaving a recess adjacent the opposite side of the bridging member, ,alever extending through the plane of the tension members and having anend pivotally received in said latter recess, said lever having itsopposite endmovable between preselected positions, said lever having arecess for pivotally supporting the second end of the tension memberspositioned to stress said tension and compression members to produce asnap spring system having an axis of maximum stress, and a reciprocableplunger engageable with said lever to move said second end of thetension members through the axis of maximum stress to actuate the snapspring system.

7. In a snap action device, the combination of a snap spring systemcomprising a first stressed member and a second stressed member mountedat one end and connected at their opposite ends to form an end free tomove between preselected positions with a snap action,'a bracket formounting said spring system, said bracket having mounting portionsextending generally outwardly from each side of the spring system and abridging portion interconnecting said mounting portions, means forrigidly supporting each of said mounting portions, one of said mountingportions having a recess on one side of the bracket pivotally receivingthe mounted end of one of the stressed members, said other mountingportion having a recess on the opposite side of the bracket, a leverextending through the plane of the other stressed member and having anend pivotally received in said latter recess, said lever having a recessfor pivotally supporting the mounted end of the other stressed memberpositioned to stress said members to form a snap spring system having anaxis'of maximum stress and a reciprocably mounted plunger engageablewith said, lever to of a support, a bracket mounted on said support, '15move the mounted end of one of the stressed members through the axis 01'maximum stress'to actuate the snap spring system.

8. In a snap action device, the combination of a support, a brackethaving portions oflset with respect to one another and a bridgingportion interconnecting said onset portions, means acting between eachportion and the support for rigidly supporting said portions on thesupport, a lever movable between preselected positions having one endpivotally mounted on one of said portions and extending in substantiallyparallel relation with said bridging portion and having its opposite endin spaced substantially parallel relation with said other portion, asnap spring system comprising a first stressedmember and a-secondstressed member interconnected at one end to form an end free to movebetween preselected positions with a snap action, the opposite end ofthe first stressed member being pivotally supported on the other of saidportions on the opposite side of the bridging member, and the oppositeend of the second stressed member being pivotally supported by saidlever to stress said members to form a snap spring system having an axisof maximum stress, and plunger means engageable first and second slots,means integral with said terminal members adapted to coact with thehousing to position the terminal members wth respect thereto, saidterminal members being insertable in said housing through the open sidethereof, a spring member having a, contact inovmounting said firststressed member in a stressed condition, a bracket defining a terminalaccessible with the lever to move said second stressed memher throughthe axis of maximum stress to actuate the snap spring system.

9. In an electric snap switch the combination of a housing of insulatingmaterial including a cover plate and a body with an open side normallyclosed by the cover plate, said housing having apertures thereinadjacent the body-cover from the exterior of the housing shaped to havea portion snugly received in said recess and a portion received in saidthird slot to rigidly suport said bracket in said housing, said bracketbeing shaped to support said second stressed member in a stressedcondition, and to form with said stressed members and said actuatingmember a snap spring system having an axis of maximum stress, saidbracket pivotally supporting said actuating member so that said bracket,said actuatin member and said spring member form an assembly insertableas a unit into said housing through the open side thereof, and meansmounted on said housing and engaging said actuating member to move saidfirst stressed mem- A -ber relative to the mounting of the secondstressed interface, a reciprocable plunger shaped to be received in oneofsaid apertures, terminal members to be received in the other of'saidapertures, two of said terminal members'having stationary contactsattached thereto, each of said apertures having an open side at saidbody-cover interface whereby said terminal members and said plunger areinsertable into said housing through said open side of the housing, saidtwo terminal members being secured in said housing by transverselyextending lugs on said terminal members engaging recesses formed in saidcover plate and in said body portion, an actuating member pivotmember onthe bracket and thereby move snap spring system through its axis ofmaximum stress whereby said free end moves between the first mentionedterminal members with a snap action. l

11. In a self-return'snap acting device, the combination of a snapspring system comprising a first stressed member and a second stressedmember forming tension and compression members, mounted at one end andconnected at their opposite ends to form an end free to move betweenpreselected positions with a snap action, a bracket for mounting saidspring system having mounting portions extending generally outwardlyfrom each side of the spring system, means for rigidly supporting eachof said mounting portions, one of said mounting portions having a reallysupported by a third of said terminal members and engageable by saidplunger, a spring member insertable in said housing through the openside formed of a resilient metallic strip, said spring member havingspaced side portions comprising elongated tension elements and havingend portions connecting said tension elements, one of said spring memberend portions having an inwardly extendin compression element, saidspring member being so fitted within said housing and its parts soproportioned and so dimensioned that its compression element ispivotally supported upon said actuating member and the end portionopposed to said compression element is pivotally supported by said thirdterminal member to stress said tension elements in tension whereby, whensaid plunger is depressed,

cess on one side of the bracket pivotally receiving the mounted end ofone of the stressed members, said other mounting portion having a recesson the opposite-side of the bracket, a movableleverextending through theplane of the other stressed member, said lever having an end pivotallyreceived in said latter recess, said lever having a portion .with arecess for pivotally supporting the mounted end of the otherstressedmember, spaced stop means engageable with said lever to limit movementof said recessed portion between opposed positions disposed on one sideof a line defined by the pivotally mounted end of the lever and saidfree end, said positions also being disposed on opposite sides of astraight line passing through the mounted end of said one stressedmember and said free end, said stressed members and mounting meansdefining a spring system normally biasing said lever to urge saidportion to one of said opposed positions,

and a plunger. operative against said lever to move said portion fromsaid one opposed position to the other opposed position to move themounted end of one of the stressed members past the mountedend of theother stressed member to actuate said spring system, said portion uponrelease of 'force on said plunger returning to said one opposed positionthrough biasing action of said spring, system to again actuate thespring system.

12. An electric snap switch, comprising a housing including a coverplate and a body with an open side normally closed by the cover plate,said housing having first, second and third spaced slots opening at thebody cover interface, terminal members shaped to be received in saidfirst and second slots, means integral with said terminals adapted tocoact with the housing to position the terminals therein, said terminalsbeing insertable in said housing through the open side thereof, a springmember having a contact movable between said terminal members, saidspring member having an axis of maximum stress and being formed from aresilient metal strip, said spring member having the general shape of arectangular frame comprising long sides and short sides interconnectingadjacent ends of the long sides, one of said shorter sides having aportion extending inwardly of said frame between the long sides, abracket definin another terminal member and shaped to be re ceived insaid third slot and supporting one of said short sides, an actuatingmember shaped to support said inwardly extending portion to stress saidlatter portion in compression and said long sides in tension, saidbracket pivotally supporting said actuating member so that said bracket,said actuating member and said spring form a 12 terminals bein'ginsertable in said housin through the open side thereof, a spring memberhaving a contact movable between said terminal members, said springmember having an axis of maximum stress and comprising spaced tensionmembers interconnected at opposite ends, one of said ends being free, tomove between said terminals with a snap action, a compressionmemberhaving an end integrally interconnected with said free end, a bracketdefining another terminal accessible from the exterior of the housingshaped to be received in said third slot to support the opposite end ofsaid tension members, a rigid actuating member pivoted on the bracketand supporting the opposite end of said compression member, saidbracket, said actuating member and said spring forming a unit insertablein said housing through the open side thereof, means disposed betweensaid bracket and said housing to position said bracket therein, and aplunger mounted on said housing and engaging said actuating member tomove said compression member relative to tension members through theaxis of maximum stress and thereby eiiect snap movement of said movablecontact between said I first mentioned terminal members.

unit insertable in said housing through the open side thereof, and meansextending through said said housing having first, second and thirdspaced slots opening at the body interface, terminal members shaped tobe received in said first and second slots, means integral with saidterminals adapted to coact with the housing to'position the terminalswith respect thereto, said OSCAR H. KAMINKY.

REFERENCES CITED The following references are of record in the file ofthispatent:

UNITED STATES PATENTS Number Name Date 1,282,816 Guett Oct. 29, 19182,157,156 Abendroth May 9, 1939 2,170,748 Eaton Aug. 22, 1939 2,228,522Johnson Jan. 14, 1941 2,228,523 Johnson Jan. 14, 194i 7 2,235,382 MillerMar. 18, 1941 2,332,911 Hausler Oct. 26, 1943 1 2,368,679 Popp Feb. 6,1945. 2,370,479 Meyer -1 Feb. 27, 1945 2,374,986 Fetter May 1, 19452,403,051 W Christensen July 2, 1946- 2,417,169 Kaminky Mar. 11, 1947

